1. Field of the Invention
This invention relates to alternating pressure pads, and in particular alternating pressure pads of the kind used in prevention and management of decubitus ulcers in bedridden patients.
2. Description of the Prior Art
The formation of decubitus ulcers, commonly known as bedsores, results from, amongst other things, the pressure applied to certain portions of the skin of a bedridden patient. In addition, it is well known that should the lower reflex arc be broken by, for instance, lesion of the spinal cord or of nerve roots, decubitus ulcers of unusual severity and rapidity of onset are likely to develop. It is known to meet the requirement for the prevention and management of decubitus ulcers with an alternating pressure pad comprising two sets of alternately inflatable cells. The alternately inflatable sets of cells are interleaved so that the patient is supported on one inflated set of cells whilst the other set is deflated. In this way, substantially all parts of the patient body resting on the pad or mattress experience pressure relief at regular intervals. The duration of the inflation and deflation cycles may last from under two minutes for a gentle massaging effect to over twenty minutes.
The comparative advantages of different sizes and shapes of inflatable cells in such an alternating pressure pad are well known. Ideally, support provided by a given region of a pad should not be effected by the pressure applied by a patient to adjacent regions. This therefore suggests that each cell should have a relatively small width. On the other hand, each inflatable cell should have a substantial height (in the support direction of the patient), to allow a substantial amount of depression of each cell, for example for supporting heavy patients or the larger bony protuberances of even relatively light patients.
GB-B-2233552 describes an alternating pressure pad with a relatively tall cell structure which meets these conflicting requirements.
In order to maximize the pressure relieving effect on a bedridden patient, the pressure within the inflated cells supporting the patient should be as low as possible. However, it is important that no part of the body of the patient being supported depresses individual cells of the pad or mattress so much as to make contact with any underlying support surface. Sensors have been proposed which will detect when a patient's body rests against an underlying surface, and will automatically in response increase the pressure in the supporting mattress. GB-B-2233551 describes such a sensor arrangement.
One problem which is occasionally experienced with high profile alternating pressure mattresses of the kind described in GB-B-2233552 is when a portion of a patient's body slips between two adjacent inflated cells of the pad (in the position of an uninflated cell) and then rests against the underlying supporting surface. This problem arises especially when a patient is in the sitting position on the bed and can be in particular a problem for orthopedic patients under traction.
The present invention is designed to alleviate problems which can arise in this way.